Rock around the clock: Zircon crystal is oldest piece of Earth

A 4.4 billion-year-old zircon crystal from the Jack Hills region of Australia is pictured in this undated handout photo obtained by Reuters on Feb 23, 2014. -- PHOTO: REUTERS

WASHINGTON (REUTERS) - To put it mildly, this is one gem of a gem.

Scientists using two different age-determining techniques have shown that a tiny zircon crystal found on a sheep ranch in western Australia is the oldest known piece of our planet, dating to 4.4 billion years ago.

Writing in the journal Nature Geoscience on Sunday, the researchers said the discovery indicates that Earth's crust formed relatively soon after the planet formed and that the little gem was a remnant of it.

Mr John Valley, a University of Wisconsin geoscience professor who led the research, said the findings suggest that the early Earth was not as harsh a place as many scientists have thought.